Denver – A look of concern grew across Gretchen Bunn’s face as she thought about what might happen Monday when Democrats come to town for the second time in a century.

Will there be traffic jams, protesters, even riots, worried the saleswoman at Rockmount Ranch Wear, standing amid floral western shirts and cowboy boots.

It’s anyone’s guess what the four-day Democratic National Convention will mean for the city with 50,000-plus attendees and the glare of national and international media. But it’s clear what city boosters want to project. Just as they landed their first Democratic convention in 1908 to prove that Denver had morphed from cow town to cosmopolitan city, they are eager to show off a city transformed once again.

This time, they are selling a “new West” city that has emerged from the boom-and-bust petroleum era into a center of environmentalism, embracing renewable energy with the same gusto as it once welcomed oil speculators.

“Denver has grown up,” says John Hickenlooper, the city’s mayor. “Back in the late 1970s and early 1980s, energy was really the only game in town.”

Denver’s new green sensibilities will be felt – whether they like it or not – by conventioneers. Mayor Hickenlooper has challenged organizers to make the Democratic National Convention (DNC) the “greenest convention in the history of the planet.” That means a lot of organic foods, as many as 900 volunteers dedicated to making sure everyone recycles, 1,000 bicycles available to the delegates, and a push to offset the convention’s carbon emissions with investments in alternative-energy and other green ventures.

“We are doing as much or more than other cities” for the environment, says Michele Weingarden, director of Greenprint Denver, the mayor’s initiative to make the city a beacon of environmentalism. “This is a chance to show that we are a green convention town.”

But fossil fuels remain a major player here today and the natural-gas industry is booming across Colorado. In the metro region alone, traditional energy companies employ 14,560 people, making fossil fuels the second-largest industry in the area, according to the Metro Denver Economic Development Corporation. The government is the region’s largest employer.

But renewables are catching up and now employ 13,941 people in the nine counties that make up the Denver region.The renewable-energy lab’s funding rises and falls with the economy and price of oil, says lab spokesman George Douglas. These days have been good for renewable research.

Last month, Mr. Douglas strode from building to building, explaining how their scientists were figuring how best to turn corn stover, the postharvest remains of the corn plant, into ethanol. In another building, solar panels were being perfected. At one point he stopped to see if there were enough plastic-wrapped safety goggles for groups of Democratic delegates expected to the lab this week.

From geologist to greenie

Hickenlooper moved west in 1981 along with thousands of other exploration geologists drawn by the thriving oil industry that would come to define Denver.

“We were like lemmings,” he joked. When oil crashed, many migrated elsewhere and left the new office buildings vacant that shot up just years before.

But Hickenlooper stayed and did what Denverites before him have done to ride out the low periods that punctuate the city’s story line. He reinvented himself, and his transformation seemed drawn straight from Denver’s history books: he opened a saloon (the city’s first building was a saloon). It was a microbrewery and restaurant, to be more precise, and would eventually become the linchpin for redeveloping the city’s lower downtown neighborhood (now called LoDo), which was just a collection of vacant warehouses and flophouses when his brewpub opened in 1988.

“The great thing about Denver and all of the Rocky Mountain West is that it doesn’t matter out here who your parents were or your grandparents were, it matters who you are and how hard you are willing to work to achieve your dreams.... And that’s a liberating sensation to have in a community,” he says.

The redevelopment of LoDo is one of Denver’s success stories and part of its efforts to diversify its economy. The area was helped along by the development of nearby Coors Field, and the Pepsi Center where the Democrats will converge.“When we first moved down here there were practically more pigeon occupants than people,” says Joyce Meskis, owner of the independent Tattered Covered bookstore that opened downtown in 1994. Today, new loft-style condos are rising all around the lower downtown area and the development has brought many new residents, including Ms. Meskis, here.

“The life it’s brought, the energy, just the reinvigoration of the city feels good. When you have the preservation of the urban core with its cultural architecture with the legacy of that it’s something special,” she says.

Historian Thomas Noel, who has penned many books on Colorado, says if he were writing a new chapter on the city it would be called “Return to downtown.”

Denverites have rediscovered a city that was essentially one big skid row until the 1990s when developers started moving in, opening restaurants and converting buildings into lofts, says Mr. Noel.

“Almost from the beginning of Denver’s history, there was suburbanization. Now for the first time we see wealthy people moving downtown. The core city is actually growing,” he says.

Old economy versus new

The economic transformation isn’t as smooth or simple as some would like.

The real estate market here has felt the impact of a nationwide downturn, but a new boom in the traditional energy sector has shielded the city from the woes much of the country is feeling, says Doug Jeavons, an energy analyst with BBC Research & Consulting in Denver. “There’s a bit of déjà vu for those who remember the early 1980s,” he says.

This is a point Meg Collins, president of the Colorado Oil and Gas Association, is eager to emphasize. A recent study conducted by Cushman & Wakefield’s Denver office showed that oil and gas contributed to 37.5 percent of the 2.5 million square feet in new and expanded downtown Denver real estate in 2007.

Oil and gas is still the No. 1 economic contributor to the state, adding $23 billion to the economy annually and employing some 70,000 people, she says. But the tide is turning sharply against the traditional fossil-fuel business as environmentalists are newly invigorated with a Democratic governor and general assembly.

“We are a huge economic contributor to this state and as a reward for that contribution we are facing this complete overhaul of the oil and gas regulation,” she says, referring to the ongoing revision of rules governing how oil and gas operates throughout Colorado.

“There is an enthusiasm for diminishing this industry,” says Ms. Collins. “You’ve got different values going on in the state.... [Y]ou’ve got areas outside Denver that were once farmland that are now becoming housing development where there is oil and gas development.”

As another wave of newcomers come West for the dramatic landscape, says Mr. Jeavons, more tensions can be expected over the rising pace of energy exploration. These newcomers aren’t coming to get rich – many already are. And they don’t want to see a gas rig standing in the way of their Rocky Mountain view.

“Attitudes are different here than they were 20 years ago,” he says. “There is much more public pressure now than there was 20 years ago to better manage” the exploration of fossil fuels.

The weight of the past

When Denver was preparing for the 1908 Democratic convention, its silver rush had ended.

The High Plains region that runs up against the Rockies had turned to agriculture and even tourism. The year before the convention, Denver rushed to build one of the country’s most magnificent civic halls, second only to Madison Square Garden at the time, to entice party bosses to host their convention here.

“We have a real sense of ‘if you build it they will come.’ That was true in 1908 and its very true today,” says William Convery, state historian with the Colorado Historical Society and a fourth generation Denverite.

The parallels between the 1908 convention and this year’s shouldn’t be drawn out too far, says Mr. Convery. Both can be seen as showcasing different stages of the city’s transformation, but there are differences, too. Since 1908, there’s been a civil rights movement and women’s rights movement, black and Hispanic mayors. Major league sports teams call the city home.

Convention planners may have also been drawn to the city to boost the party’s nominee, Barack Obama, in Mountain West states that have changed from red to purple on the political spectrum as liberal young newcomers and minorities continue to move here.

The convention will be somewhat of a test for Hickenlooper, who came into office with a tremendous popularity in 2003 and was reelected in 2007.

Can he keep it safe, deal with the protesters, make good on his green challenge, and ensure a stress-free four days for Denverites who jealously guard their laid-back lifestyle?

The mayor has won accolades for his efforts to green the city – he aims to decrease its greenhouse-gas footprint by more than 10 percent and is a booster of the FasTracks project to bring 119 miles of light rail tracks to the area. But he also faces some criticism for not pushing other counties in the region to follow Denver’s lead.

Jeremy Nicholas, director of Rocky Mountain Clean Air Action, says that Denver’s green efforts are being erased “by cities like Aurora and other suburbs that aren’t doing anything about environmental issues.”

As natural gas drilling continues to boom north of Denver, Mr. Nicholas worries that the emissions will further degrade the city’s air quality. “[It’s] this huge stew that we’re all in.”

Hickenlooper says that other counties are moving at different paces, but that all the elected officials in the region want to help improve Denver area’s air quality, which the Environmental Protection Agency said violated the eight-hour federal health-based standard in 2005, 2006, and for the first three quarters of 2007.

Colorado Oil and Gas Association’s Collins says that environmentalists shouldn’t be too quick to point out the implications of increased gas exploration and mining.

“Let’s not lose sight of the fact that we’re going to be a carbon economy for decades. We can all work together, but you don’t have to bash oil and gas to promote renewables,” she says.

The Mile-High City

As of 2007, a population of 588,349 made Denver the 26th most populous city in the US. Hispanics make up 34.8 percent and African-Americans, 9.9 percent.

• Nicknamed “Mile-High City” because its official elevation is exactly one mile above sea level.